1) Field of the Invention
The invention relates to a differential pressure sensor, and more particularly relates to a pressure sensor that can detect decompression within a compartment, such as an aircraft cockpit, without having to measure pressures across the bulkhead, that is, a partition that divides the cockpit and another compartment of the aircraft.
2) Description of Related Art
The United States Government, and in particular, the Federal Aviation Administration (FAA), in response to recent terrorist attacks in the United States and elsewhere in the world, has implemented various regulations designed to prevent terrorists from appropriating mobile platforms such as aircraft, buses, and subways. For example, the United States Government now requires aircraft to include secure cockpit doors that are resistant to terrorist intrusion in an effort to prevent terrorists and unauthorized personnel from gaining access to the cockpit and to the controls of the aircraft. Security systems with enhanced safety features for cockpit doors exist to prevent unauthorized entry into an aircraft cockpit or onto a flight deck and to comply with governmental regulations. Known security systems included cockpit door frame reinforcements, bulletproof materials, improved cockpit door latches and two-sided pressure sensor/aneroid systems. However, while known security systems, such as cockpit door and door frame improvements, adequately prevent access to the cockpit and other restricted areas, conventional reinforced door latch mechanisms are not suitable for use with an aircraft due to pressurization of aircraft cabins and cockpits.
Aircraft cockpits and cabins are pressurized due to the altitude at which most commercial aircraft fly, and they are maintained at a certain pressure to provide crew and passengers with a safe and agreeable flight. However, under certain conditions, the cockpit and cabin may lose pressure and experience a depressurization or decompression situation. Forces associated with such depressurization or decompression situations typically occur very rapidly and can cause the cockpit and cabin to change structurally. Aircraft are required to fly with the cockpit door securely locked to prevent intrusion into the cockpit. However, under a cockpit depressurization or decompression situation, the cockpit door must be opened to allow venting of the cabin area and relieve the now higher pressure on the cockpit/cabin bulkhead therein. Due to the size and rate of the forces exerted on the cockpit door and its associated frame/support structure during depressurization or decompression, conventional latches can jam and prevent the cockpit door from being opened. Moreover, many known pressure sensor/aneroid systems are two-sided in construction, that is, they can only detect a pressure loss within the cockpit by measuring pressure across the bulkhead which is the divider between the cockpit and the passenger cabin area. These known two-sided systems can be problematic in that an individual on the passenger side of the bulkhead can initiate a false trip to the system, which allows the cockpit door to be free to open.
Accordingly, there is a need for an improved security cockpit door pressure sensor that can detect decompression within a compartment, such as an aircraft cockpit, without having to measure pressure across the bulkhead, while still allowing a compartment or cockpit door to be adequately locked to prevent intrusion into the compartment or cockpit during flight, and that does not have the problems associated with known security systems.